Barcelona were dismayed with the performance of official Wolfgang Stark, believing the German made questionable decisions regarding a number of incidents.

The club's main criticism stirs from the second-half collision of Barcelona pair Javier Mascherano and Jordi Alba, the clash of bodies leaving the two defenders prone on the ground. However, Stark let the game continue.

"The club has written to Uefa due to a series of incidents on the pitch in the understanding that objectively speaking it was evident that the referee did not apply the rules of the game," Barcelona's spokesman Toni Freixa said after a meeting of the club's board.

"When two players from the same team are on the floor the referee should stop the match, which did not happen.

"What's more he then obliged them to leave the pitch, in contravention of the rules.

"It is an incident that is sufficiently serious in a competition like the Champions League to bring to Uefa's attention so that it does not happen again."

Another incident to earn the ire of the Barcelona faithful was Zlatan Ibrahimovic equaliser in the 79th minute, the Swede levelling the match at 1-1 from an offside position.

But once again, Stark and his officials missed the incursion and the goal stood.

"We are fully conscious of the possibility of errors in refereeing and we do not consider ourselves badly treated," Freixa said.

"But it surprises us that in a high-level competition a referee does not know the rules.

"We are not judging the work of referees but the basic principle that a judge should know the law. We hope it does not happen again."